(a) Field of the Invention
The present invention relates to a syndiotactic polypropylene resin composition. More particularly, the present invention relates to a syndiotactic polypropylene resin composition having excellent moldability (e.g. excellent fluidity and mold releasability), good optical properties (e.g. good transparency and gloss) and good mechanical properties (e.g. good rigidity and impact resistance).
(b) Description of the Prior Art
Syndiotactic polypropylene has excellent transparency, impact resistance, electrical properties, etc. but has a problem of low hardening rate, that consequently causes poor moldability (particularly, poor injection moldability).
The hardening rate of crystalline polypropylene can be increased by, for example, addition of a nucleating agent. When there is added to crystalline polypropylene a known nucleating agent typical examples thereof are organic nucleating agents such as aromatic carboxylic acid metal salt (e.g. GBA), sorbitol derivative (e.g. Gelall MD), organic phosphoric acid salt (e.g. NA-21) and the like and inorganic nucleating agents such as talc and the like!, an increased crystallization rate is obtained and, in the case of isotactic polypropylene, improved transparency is obtained in many cases but the transparency is not sufficient. In the case of syndiotactic polypropylene, the crystallization rate after addition of the above nucleating agent is not sufficient and, moreover, addition of the nuceating agent results in reduced transparency.
It is known that addition of diamine/monocarboxylic acid condensate to isotactic polypropylene gives improved slip property and anti-blocking property of film.
Japanese Patent Application Kokai (Laid-Open) No. 220268/1994 discloses a composition obtained by adding a diamine/monocarboxylic acid/polybasic acid polycondensate to isotactic polypropylene. It is described in the literature that the composition has improved fluidity and gives a molding of improved heat resistance and impact resistance
Isotactic polypropylene, which has a high crystallization rate and good moldability, hardly has a problem of poor mold releasability associated with low crystallization rate. Therefore, the above literature aims at improved fluidity and improved heat resistance and impact resistance of molding.
Meanwhile, syndiotactic polypropylene, although having excellent properties (e.g. excellent transparency, impact resistance and electrical properties), has a low crystallization rate and resulting poor moldability, which is an inherent problem of syndiotactic polypropylene and must be improved when syndiotactic polypropylene subjected to injection molding. (This problem is not present in isotactic polypropylene.)
The object of the present invention is to improve the poor moldability of syndiotactic polypropylene, and provide a molding having good transparency.